Electrochemical performance and stability of La0·5Sr0·5Fe0·9Nb0·1O3-δ symmetric electrode for solid oxide fuel cells

Symmetric solid oxide fuel cells (SSOFCs) based on the Co-free La0·5Sr0·5Fe0·9Nb0·1O3-δ (LSFNb) perovskite oxide are prepared by the sol-gel method. The structural stability and catalytic activity of LSFNb as an electrode for both the hydrogen oxidation reaction and oxygen reduction reaction are studied. We show that Nb substitution in La0·5Sr0·5FeO3-δ greatly improves its chemical and phase stability under reducing atmosphere. At 800 °C, the area specific polarization resistances (ASRp) of La0·5Sr0·5Fe0·9Nb0·1O3-δ symmetric cells are as low as 0.06 and 0.24 Ω cm2 in air and wet H2 (3% H2O), respectively. LSFNb based electrolyte-supported SSOFCs deliver peak power densities of 1000 mW cm-2 at 850 °C in wet H2/air. In addition to high performance, the symmetric cell shows stable power output under load (measured for 140 h at a current density of 520 mA cm−2, 800 °C) under air/humidified H2 operation, indicating that LSFNb may be a particularly promising new symmetric electrode material for solid oxide fuel cells.